muirhead



(No Model.) 2 Sheets-Sheet 1. A. MUIRHEAD.

SUBMARINE DUPLEX TELEGRAPH. No. 327,097. Patented Sept. *29, 1885.

.417 would d z 'fubrlal azza.

Maw;

(No Model.) 2 Sheets-Sheet 2.

A. MUIRHEAD.

SUBMARINE DUPLEX TELEGRAPH.

No. 327,097. Patented Sept. 29, 1885.

fails N. PETERS, Phnlo-Lilhogrnphcn wnmm lm n. c.

UNITED STATES PATENT OFFICE.

ALEXANDER MUIRHEAD, OF NORWOOD, COUNTY OF SURREY, ENGLAND.

SUBMA RINE DUPLEXTELEGRAPH.

SPECIFICATION foaming part of Letters Patent No. 327,097, datedSeptember 29, 1885.

Application filed December 18, 1884.

tem, as described in Letters Patent of the United States No. 234.490.granted to me on the 16th day of November, 1880, or on any otheranalogous system of working.

In the accompanying drawings, Figure 1 is a diagram showing the improvedarrangement of apparatus for carrying out the invention described in theabove Letters Patent, and is substantially a reproduction of Fig. 3 ofthe drawings accompanying thesame; and Fig.2 is a diagram showing thearrangement and modification of that apparatus for carrying out thepresent invention. Fig. 3 shows the application of the present inventionto both sides of the differential circuit."

In Fig. lot the drawings, S' and S are the two sets of condensers,placed, respectively, between the key K and the cable 0 and the key andthe artificial cable- A L.

As has been stated in the specification forming a part of said LettersPatent No. 234,490, it has been found practicable to establish andmaintain a balance without using bridge-wires, by adjusting the capacityof the condensers S S relatively to each other; but I have sincediscovered that on very long cables, such as those recently laid betweenOanso, Nova Scotia, and Waterville, Ireland, (the Bennett- Mackaycables,) it is insufficient and extremely difficult to effect andmaintain in practice an exact balance by merely having the condensers SS (sending-condensers) adjusted for capacity. In order to effect abalance sufficiently exact for the purpose of obtaining the greatestpossible speed of working, it is necessary not only that the capacity ofthe condenser S placed between the key K and submarine cable G, shouldbe of the required ratio (N0 model.)

to that of the condenser S between the key K and the artificial cable AL, but also that their times of charging and discharging should be thesame.

As it is practically impossible to construct or build up a number ofsets of large condensers even out of exactly the same materials, so thattheir rates of absorption of charge shall be the same throughout, Iresort to the following device, which is the snbjectof this invention,and which is illustrated in Fig. 2.

The condensers S S in Fig. 2 correspond with those n1 :rked S S in Fig.1 of the drawings of Letters Patent No. 234.490. A rheostat, Rh, of lowresistance, adjustable to varying resistances, is interposed between thesig naling-key K and the condensers S and S The cable 0 andtheartificial cable A L are connected with these condensersin the mannershown, and a condenser, S, and receiving-instrument R are inserted inthe circuit between the real and artificial cables.

B represents the battery, and E the earth.

To -one ofthe two condensers, preferably to the smaller of the two-say Sel attach another and supplementary condenser. S, which is subdividedinto small parts. and I insert between one terminal of it and oneterminal of S aset of resistance coils (marked H R in the diagram) ofhigh resistance-say of one thousand to one hundred thousand ohms'and Iconnect the other terminal of S by a simple wire with the correspondingterminal of S as shown.

In effecting the balance the artificial cable A L is first of all madeelectrically equal to the cable 0. The condensers S and S are theninserted and their capacities adjusted by means of the subdividedcondenser S After obtaining in this way the nearest balance, a slightincrease is made in the capacity of S say by one microfarad-and bytrials the amount of resistance required in the resistance-coils H R isascertained. This produces a flow of charge in the circuit of S and Stogether equal to that flowing into the condenser S".

By way of illustrating and explaining my improved method of duplexbalancing, I give the conditions required in balancing one of theabove-mentioned Mackay-Bennett cables, which are as follows: On thenortherly of the two main cables S is equal to one hundred and twentymicrofarads, S to one hundred and twenty microfarads, S to fifteenonehundredths of amicrofarad, and the resistancecoils H R to one hundredthousand ohms. In this case the combination of the small capacity in Swith the resistance of the coils H R produces a flow of charge of slowerrate,which superposed upon thatot' the condenser S produces the sameeffect as the charging and discharging of the condenser S.

Under certain conditions it has been found desirable to provide for anadditional adjustment through the condenser S, Fig. 2, in the actualline, as well as through the condenser S in the artificial line. In suchcases the condenser S, Fig. 2, is provided with a resistance-circuitcomposed of a resistancecoil and a supplementary condenser preciselysimilar to those used in connection with the condenser S and shown by HR and S", respectively, in Fig. 2. The adjustment is then effectedthrough both condensers, instead of through one, as before. Thisarrangement is represented in Fig 3, in which S and S are the maincondensers in the circuit, S and S the adjustable supplementarycondensers, and, H 1% and H R the resistancecoils in eitherresistancecircuitsurroundingthe main condensers. By way of illustratingand explaining the method of duplex balancing shown in Fig. 3, I givethe conditions required in balancing the southerly of the twoabove-mentioned cables at the station at Waterville, Ireland. Here S isequal to seventy-nine microfarads, S to one microfarad, and H R tothirteen thousand ohms. S" is equal to eighty microfarads, S equal toone and fifty-one one-hundredths microfarads, and H R to thirty-eightthousand ohms. The effect produced is substantially the same as before,and is in some cases more favorable.

The present invention is not limited to the hereinbefore-describedsystem, but is applicable to any other system of working in which it isrequired to balance one cable against another by means of condensers,either in the case of double-cored cables or cables under separatearmatures.

I claim as my invention-- l. The combination, substantiallyas'hereinbefore set forth, in an electrical or telegraphic circuit, ofan adjustable condenser in the circuit, an electrical circuitsurrounding said condenser for modifying the capacity of the same, anartificial resistance in said modifying-circuit, and a supplementarycondenser also in said modifyingcircuit, for the purposes set forth.

2. The combination, substantially as hereinbefore set forth, in anelectrical or telgraphic circuit, of the receiving-instrument, the adjustable rheostat, the separate condensers in the circuit, oneconnecting with the actual and the other with the artificial orcompensating line, the adjustable supplementary condenser, and theadjustable resistance-coil in connection with one of said condenserswith the key and battery and the condenser in the bridge or circuitbetween the actual and the artificial lines.

3. The combination, substantially as hereinbefore set forth, in anelectrical or telegraphic circuit, of the receiving-instrument, theadjustable rheostat, the separate condensers in the circuit, oneconnecting with the actual and the other with the artificial orcompensating line, the electrical circuits surrounding said condensersfor modifying the capacity of the same, the adjustable supplementarycondensers, and the adjustable resistance-coils in saidmodifying-circuits with the key and the battery and the condenser in thecircuit between the actual and the artificial line.

In testimony whereof I have hereunto subscribed my name this 10th day ofDecember, 1884.

ALEXANDER MUIRHEAD.

Witnesses;

E. T. RIoE, Jr., J. MUIRHEAD.

